Treatment of fractures and nonunions of the proximal femur collectively have an incidence approaching 300,000 per year in the United States and an associated annual health care burden approaching ten billion dollars. Current implants for these injuries fatigue causing discomfort, risk of further injury and need for reconstruction.
US patent application publication 2005/0010226 describes a locking plate that fastens to the bone using bone anchors. The bone anchors extend into the femoral head, contacting each other at their tips in a truss formation with all of the bone anchor holes lying in the same longitudinal axis on the plate. There are no provisions for managing fracture extension into the femoral neck or isolated vertical femoral neck fracture. An additional concern with this implant is that the proximal body is slender with only a single screw slot in the greater trochanter. This may prevent adequate capture of the greater trochanter in the presence of coronal splitting, a common occurence as documented by Russell in “Skeletal Trauma”. Russell T A, Taylor J L. Subtrochanteric fractures of the femur. In: Browner, B D, Levine A M, Jupiter J B, Trafton P F, Eds. Skeletal Trauma. Philadelphia: WB Saunders, 1992: 1883-1925.
With intertrochanteric and subtrochanteric extension of a femoral neck fracture cancellous lag screw fixation is not possible. This is because fixed angle constructs are a requirement and sliding compression is undesirable here. Vertical femoral neck fractures are also poorly managed with multiple cancellous lag screws due to the extremely high shear forces across these fractures. A fixed angle construct is more appropriate here as well.
In addition current, proximal femur locking plates do not allow for an ideal screw geometry in the femoral head. As a result, some plates in use have been shown to cause the bone anchors to be exposed as they pass through the greater trochanter and into the femoral head but not through the neck. Further, the most proximal portion of the plate may protrude well above the greater trochanter portion of the femur when applied to femoral neck fractures which may create discomfort to the subject treated with the plate. Aminian et al, Vertically Oriented Femoral Neck Fractures: Mechanical Analysis of Four Fixation Techniques, Orthopedic Trauma. 2007, 21: 544-547.
Thus what is needed is an improved system and device to provide an improved treatment for nonunions and fractures of the proximal femur.
Additional objects and advantages of the present invention will be apparent in the following detailed description read in conjunction with the accompanying drawing figures.